Optical fiber connectors (“connectors”) are devices used to optically connect one optical fiber to another, or to connect an optical fiber to another device such as an optical transmitter or an optical receiver. An optical fiber cable typically carries the optical fiber, which has a core section with a relatively high index of refraction and in which most of the light is carried, and a cladding section with a relatively low index of refraction that surrounds the core. A ferrule in the connector supports a bare end section of the optical fiber. The bare end section has a polished end face that coincides with a front face of the ferrule. The connector and the optical fiber cable constitute a cable assembly.
An important property of a connector is its ability to provide an efficient optical connection with the optical fiber of another connector, i.e., an optical connection whereby the optical loss (also called “insertion loss”) from the light passing out of one fiber end face and into the other fiber end face is minimal. This efficiency is sometimes referred to as “coupling efficiency.” A misalignment of the end faces of the two optical fibers supported by the two connectors is one of the main sources of insertion loss. Since most of the light traveling in an optical fiber is confined to the core, the coupling efficiency between two connectors depends in large measure on the amount of offset between the cores. This offset can be due to an offset between the location of the core of the optical fiber and the true center of the ferrule (i.e., the geometric center based on an outer surface of the ferrule), also known as core-to-ferrule eccentricity (CTFE). Thus, CTFE represents the concentricity error between the core and the ferrule (“core-to-ferrule” concentricity error).
Ideally, the cores of the optical fibers supported by respective connectors are perfectly axially aligned to maximize the coupling efficiency. In practice, however, there is almost always some amount of core-to-ferrule concentricity error. It would therefore be advantageous to reduce the core-to-ferrule concentricity error on a ferrule-by-ferrule basis to improve the coupling efficiency of connectors.